Method for transmitting a message and telecommunication system

ABSTRACT

The invention relates to a method for the transmission of a message from a first to a second telecommunication terminal (CD), of which at least one is connected to a fixed-line telephone network (PTSN). The message, as a short message, is converted into short message format, a logical connection established by means of an adequately specified data connection layer (DL) and the short message transmitted in short message format, to a short message service centre (SMSC), in an adequately specified physical layer by DTMF or FSK off-hook signalling and then from said centre to the second telecommunication terminal.

[0001] The invention relates to a method for transmission of a message from a first to a second telecommunication terminal, of which at least one is connected to a line-connected telephone network, and a telecommunication system for carrying out this method.

[0002] In mobile radio networks operating according to the GSM standard, communication by means of short messages on the basis of the standard provided therefor has become successfully established in addition to the—of course far dominant—voice communication, in particular with regard to considerable cost advantages. In addition to the cost advantages, message transmission by SMS (short message service) also has utility value advantages in specific applications. Thus, reception and sending of an SMS can be realized without an acoustic annoyance for the environment, and the transmission of short messages also affords additional expression and psychological articulation possibilities compared with voice communication.

[0003] SMS is a point-to-point short message service which is realized in the context of the GSM protocol architecture at the signaling level. It comprises the transport of packet-oriented useful data from and to mobile stations. The short messages are always transported via a short message service center (SM SC) in store-and-forward operation. The service center accepts the short messages, which are not more than 160 characters long, from a mobile station as telecommunication terminal and forwards them to a second telecommunication terminal—a further mobile station or else a fax unit or the like.

[0004] The GSM standard defines a specific protocol architecture for realizing this service. This architecture is defined in the ETSI specifications and is adequately described in the literature (cf. for instance, J. Eberspacher, H. J. Vögel: “GSM Global System for mobile communication”, Stuttgart, 1997), so that a more detailed description can be dispensed with here and reference may be made to the appended list of standards/documents.

[0005] In the existing public line-connected telephone networks, such a transmission of short messages between normal telecommunication terminals (e.g. telephones) is not possible at the present time.

[0006] The invention is therefore based on the object of specifying a method and a telecommunication system which enable the transmission of short messages according to the SMS model in a line-connected telephone network (fixed network).

[0007] This object is achieved by means of a method having the features of claim 1 with regard to its method aspect and by means of a telecommunication system having the features of claim 2 with regard to its arrangement aspect.

[0008] The invention includes the fundamental concept that, without consideration of the profound system differences between mobile radio networks, on the one hand, and the known line-connected networks (fixed networks), on the other hand, the tried and tested SMS protocol architecture of the GSM standard (or else a comparable architecture of the UMTS standard) is to an extent mapped onto the fixed network and expanded.

[0009] With the specifications described below, the invention defines the transmission protocol and the physical and administrative preconditions for the transmission of short messages in the short message (SMS) format between the terminal and the short message service center. In this case, the transmission protocol is preferably defined in close accord with the protocol defined in the GSM standard. This pursues the aim of offering the transmission of short messages as a new service for the fixed network with little outlay and high compatibility with existing systems. A uniform SMS format is used in the GSM network and in the fixed network, thereby ensuring the smooth transmission of short messages between a mobile radio network that is set up and operated according to the GSM standard and the fixed network equipped according to the invention. Moreover, the path taken by this embodiment of the invention affords the considerable practical advantage that, in the specification of the SMS service, it is possible to have recourse to the greatest possible extent to the recognized, tried and tested GSM specifications that have proved reliable in the meantime.

[0010] In the physical layer, the data transmission between terminal and service center is effected by means of DTMF signaling and/or by means of an FSK (frequency shift keying) off-hook signaling specified according to ETS 300 659-1 and ETS 300 659-2. These aforementioned transmission methods can be used in any desired combinations. In particular, the terminal can perform signaling by means of DTMF and the service center can utilize FSK modulation, in which case, of course, the respective receiving unit must be adapted for the method employed.

[0011] Above the physical layer, a data link layer is specified which ensures the logical connection setup and the fitting to the GSM-SMS standard. The latter standard is defined in particular in the ETSI documents GSM04.07 (ETS 300 556), GSM04.11 and GSM03.40. In compatibility therewith, the data link layer can be freely defined in adaptation to the concrete requirements.

[0012] In accordance with one advantageous instance of the invention, the newly defined physical layer and data link layer are combined with the existing layers of the GSM-SMS protocol set. This involves the short message transfer layer (SM-TL) in accordance with ETSI document GSM03.40, the short message relay layer (SM-RL) according to GSM03.40 and 04.11 and also the connection management layer (CM) according to GSM04.11.

[0013] The last-mentioned layer CM specifically defines an additional message for the signaling of the connection state (CP-Connect), whose format is determined according to GSM04.07/chapter 11. There is also a specific definition with regard to the format of a message in the data link layer (DL). This will be discussed in more detail further below.

[0014] In a preferred application of the invention, as already indicated further above, one of the telecommunication terminals is connected to a mobile radio network that is operated according to the GSM standard or else the future UMTS standard, the connection between the two networks being established in a customary manner by a gateway mobile switching center.

[0015] A further advantageous application of the invention results if at least one of the telecommunication terminals is a cordless telephone from which or to which the short message is transmitted into or from the fixed network via a fixed station or private branch exchange operated according to the DECT standard. Modern cordless telephones are provided with the most important hardware preconditions for implementing the proposed service; in particular, they are generally equipped with a suitable display unit and means for DTMF signaling and are designed for identifying the abovementioned FSK off-hook signaling.

[0016] Advantages and expediencies of the invention emerge, moreover, from the following more detailed description with reference to the figures, of which:

[0017]FIG. 1 shows a schematic sketch of a telecommunication system according to the invention,

[0018]FIG. 2 shows an illustration of the layer model (SI model) of the configuration according to FIG. 1,

[0019]FIG. 3 shows a flow diagram for a connection setup initiated by the telecommunication terminal in accordance with one embodiment of the invention,

[0020]FIG. 4 shows a flow diagram for a connection setup initiated by the short message service center in accordance with one embodiment of the invention,

[0021]FIG. 5 shows an illustration of the setup of a message for the start of the procedure on the connection management layer, and

[0022]FIG. 6 shows an illustration of the message format on the data link layer.

[0023]FIG. 1 schematically shows the basic components of a telecommunication system according to the invention, namely a public line-connected telephone network (fixed network) PSTN, a telecommunication terminal CD connected to the latter, and a short message service center SM SC likewise connected to the fixed network. The following explanations for elucidating the invention relate to the interaction of these components.

[0024]FIG. 2 shows the associated SI layer model, above the physical layer (not illustrated here). The layer structure comprises firstly a data link layer DL specified in more detail further below and furthermore the layers known per se from the GSM-SMS standard, connection manager CM, short message relay layer SM-RL and short message transfer layer SM-TL and also - on the part of the terminal application. The protocol descriptions of the layers SM-TL, SM-RL and CM can be gathered from the ETSI documents GSM03.40 [1] and GSM04.11 [3]; in this respect, see the enclosed list of standards/documents. The basic precondition for the transmission of short messages via the fixed network PSTN is a circuit switching between the participating units (telecommunication terminals and short message service center) . It is then unimportant whether the units are connected via ISDN or an analog interface. FIGS. 3 and 4 schematically illustrate the setup of a connection proceeding from a telecommunication terminal (FIG. 3) or proceeding from the short message service center (FIG. 4). These diagrams are self-explanatory for the person skilled in the art and therefore require no further explanation here. In the case of an ISDN network, the messages are of functional type and are transmitted in the ISDN-D channel. Ringing pulses and busy signals are involved in the case of an analog network. After the setup of the connection, all the information items are transmitted between the units by FSK signaling in the voice band, specifically in accordance with the ETSI specifications ETS 300 659-1 [4] and ETS 300 659-2 [5]. FIG. 5 shows the setup of an additional message CP CONNECT, which serves for enabling the called unit to notify the calling unit of the setup of the connection. This notification is necessary in order wo 01/58185 - 7 - PCT/EP01/00502 to initiate the sequences in the CM layer. The message type coding is: 0x40 0100 0000B, and the format follows GSM04.7/chapter 11 [2]. The layer DL enables the connection manager (layer CM) to send and receive messages with the partner unit, it provides the bit error detection and realizes a mark signal for a message in the layer CM. FIG. 6 illustrates the format of a message in the data link layer. The field “mark signal” comprises a block of 80±25 bits. The field “message type” comprises one octet and contains a binary coded identification code number for the message. The coding for a DL_SMS_INFO message type is: 011H 0001 0001B. The coding for a DL_SMS ERROR message type is: 012H 0001 0010 B. The field “message length” comprises one octet and contains the binary coded number of octets of the message (with the exception of the octets of the message type, the message length and the checksum). Overall, a message length of up to 255 octets is allowed. The field “checksum” comprises one octet and contains the two compliments of the sum of all the octets in the message, starting from the “message type” octet to the end, modulo 256. In the case of a checksum error, the data link layer of the receiving unit sends a message of the type “DL_SMS_ERROR” to the (originally) sending unit. In this message, the data field is empty and the message length is set to zero. The data link layer of the sending unit must thereupon repeat the last message sent. With regard to the physical layer, it should also be noted that a half-duplex 1200 baud modulation can be WO 01/58185 - 7a - PCT/EP01/00502 used in the case WO 01/58185 - 8 - PCT/EP01/00502 of FSK signaling. In the case of DTMF signaling, each octet of a message is divided, in the data link layer, into the higher (upper) and lower nibble. Each nibble is coded with a DTMF bit. The upper nibble is sent first and then the lower nibble. In the case of DTMF signaling, the mark signal of the DL message is omitted. There are diverse combination possibilities with regard to the signaling method; in the normal case, a selection is fixedly installed in the telecommunication terminal, which selection can then no longer be altered by the user. 

1. A method for transmission of a message from a first to a second telecommunication terminal (CD) , of which at least one is connected to a line-connected telephone network (PSTN) with DTMF signaling, in which case, the SMS protocol architecture of the GSM standard or a comparable architecture of the UMTS standard is mapped onto the fixed network and expanded, the message is input as a short message, in particular via an input keypad or a touchscreen, on the first telecommunication terminal, the short message is converted into the short message format, a logical connection setup is realized by means of an adequately specified data link layer (DL), combined with a short message transfer layer (SM-TL) , a short message relay layer (SM-RL) and also a connection management layer (CM), the short message is transmitted in the short message format in an adequately specified physical layer by means of DTMF or FSK off-hook signaling to a short message service center (SMSC) and from the latter to the second telecommunication terminal, and the short message obtained from the short message service center is converted, in the second telecommunication terminal, into an output format and is output, in particular on a display unit.
 2. A telecommunication system for carrying out the method as claimed in claim 1, having a first and a second telecommunication terminal (D) and a line-connected telephone network (PSTN), to which at the first or second telecommunication terminal is connected, characterized by an SMS transmission protocol in which a data link layer (DL) is specifically defined and combined with a short message transfer layer (SM-TL), a short message relay layer (SM-RL) and also a connection management layer (CM), and a physical layer is specifically defined, and means in the first and second telecommunication terminals for implementing the SMS transmission protocol for inputting or outputting a short message.
 3. The telecommunication system as claimed in claim 2, characterized in that one of the telecommunication terminals is connected to a mobile radio network operated according to the GSM or UMTS standard, the line-connected network (PSTN) being connected to the mobile radio network via a gateway mobile switching center.
 4. The telecommunication system as claimed in claim 2 or 3, characterized in that one of the telecommunication terminals is a cordless telephone which is connected to the line-connected telephone network via a fixed station or private branch exchange operated according to the DECT standard.
 5. The telecommunication system as claimed in one of the preceding claims, characterized in that an additional message for the specific signaling of the connection state to the calling unit in the format according to GSM04.07/chapter 11 is defined in the connection management layer (CM).
 6. The telecommunication system as claimed in one of claims 2 to 5, characterized in that the format of a message in the data link layer (DL) is defined as follows: a field “mark signal”, a field “message type”, field “message length”, a field “CM layer message CP . . . ”, a field “checksum”, in this order.
 7. The telecommunication system as claimed in one of claims 2 to 5, characterized by a short message service center (SMSC) assigned to the line-connected telephone network (PSTN) and serving for the transmission of short messages in the short message format. 